Merge pull request #358 from EvgeniiG/tweak_lod_pattern

Slightly tweak the LOD pattern to ensure the geometry is always visible

Assets/ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/LitData.hlsl

 void GetSurfaceAndBuiltinData(FragInputs input, float3 V, inout PositionInputs posInput, out SurfaceData surfaceData, out BuiltinData builtinData)
 {
 #ifdef LOD_FADE_CROSSFADE // enable dithering LOD transition if user select CrossFade transition in LOD group
-    LODDitheringTransition(posInput.unPositionSS, unity_LODFade.y); // Note that we pass the quantized value of LOD fade
+    LODDitheringTransition(posInput.unPositionSS, unity_LODFade.x);
 #endif
 
     ApplyDoubleSidedFlipOrMirror(input); // Apply double sided flip on the vertex normal
 void GetSurfaceAndBuiltinData(FragInputs input, float3 V, inout PositionInputs posInput, out SurfaceData surfaceData, out BuiltinData builtinData)
 {
 #ifdef LOD_FADE_CROSSFADE // enable dithering LOD transition if user select CrossFade transition in LOD group
-    LODDitheringTransition(posInput.unPositionSS, unity_LODFade.y); // Note that we pass the quantized value of LOD fade
+    LODDitheringTransition(posInput.unPositionSS, unity_LODFade.x);
 #endif
 
     ApplyDoubleSidedFlipOrMirror(input); // Apply double sided flip on the vertex normal

Assets/ScriptableRenderPipeline/ShaderLibrary/Common.hlsl

 }
 
 // LOD dithering transition helper
-// ditherFactor should be a quantized value between 0..15/16, i.e the one provide by Unity
-// LOD1 must use this functoin with ditherFactor 0..1
+// LOD1 must use this function with ditherFactor 0..1
 void LODDitheringTransition(uint2 unPositionSS, float ditherFactor)
 {
     // Generate a fixed pattern
     // We want to have a symmetry between 0..0.5 ditherFactor and 0.5..1 so no pixels are transparent during the transition
     // this is handled by this test which reverse the pattern
-    p = (ditherFactor >= 0.5) ? (15.0 / 16.0) - p : p;
+    p = (ditherFactor >= 0.5) ? p : 1 - p;
     clip(ditherFactor - p);
 }